The invention relates to a fuel injection nozzle for internal combustion engines.Injection nozzles of this type have the advantage that the opening stroke of the valve needle is performed in a damping manner. By a corresponding coordination of the throttle passage and a return spring of the cap it can be achieved that the dampening in certain ranges of the operating performance graph is only effective over a partial stroke of the valve needle. The pressure piece which is displaceably mounted in the bottom of the cap transmits the fuel pressure directly to the piston during a prestroke and through this piston to the valve needle. Thereby, it is achieved that a prestream of a sufficiently large fuel amount is injected at the start of each injection operation.
In a known injection nozzle of this type (DE-Al 33 07 671) the pressure piece has the same diameter as the piston which is connected with the valve needle. In this embodiment it is easy to work the bore in the cap, however the prestroke of the valve needle performs practically undampened. In many cases this may undesirably influence the dampening effect of the subsequent partial stroke or may result in certain ranges of the operating performance graph in an unfavorable ratio of the preinjection amount with respect to the main injection amount.